1. Field of the Invention
The present invention generally relates to optical devices coupled to optical fibers, and particularly to optical fiber-coupled devices that can be formed in large numbers using wafer-level techniques.
2. Description of Related Art
Optical fibers have by far the greatest transmission bandwidth of any conventional transmission medium, and therefore optical fibers provide an excellent transmission medium. An optical fiber is a thin filament of drawn or extruded glass or plastic having a central core and a surrounding cladding of lower index material to promote internal reflection. Optical radiation (i.e. light) is coupled (i.e. launched) into the end face of an optical fiber by focusing the light onto the core. For effective coupling, light must be directed within a cone of acceptance angle and inside the core of an optical fiber. Because any optical radiation outside the core or acceptance angle will not be effectively coupled into the optical fiber, it is important to precisely align the core with an external source of optical radiation.
A fiber optic coupler for coupling optical radiation between an optical device and an optical fiber is disclosed in U.S. Pat. No. 6,328,482 B1, issued Dec. 11, 2001, entitled MULTILAYER OPTICAL FIBER COUPLER, which is incorporated by reference herein. The '482 patent discloses, inter alia, a multiplayer optical fiber coupler that includes a first layer that defines a fiber socket in which an optical fiber is situated, and a second layer coupled to the first layer.
It would be an advantage to provide optical fiber-coupled devices that provide functions such as filters, switches, and multiplexers/demultiplexers, and in which the optical fiber is integrated into the optical device.
Conventional optical devices generally require costly and time-consuming alignment steps to ensure efficient coupling to optical fibers. For example, one conventional practice for making a fiber-pigtailed transmitter is to assemble an edge-emitting laser diode, an electronics circuit, a focusing lens, and a length of optical fiber and then manually align each individual transmitter. To align the transmitter, the diode is turned on and the optical fiber is manually adjusted until the coupled light inside the fiber reaches a predetermined level. Then, the optical fiber is permanently affixed by procedures such as UV-setting epoxy or laser welding. This manual assembly procedure is time consuming, labor intensive, and expensive. Up to 80% of the manufacturing cost of a fiber-pigtailed module can be due to the fiber alignment step. The high cost of aligning optical fiber presents a large technological barrier to cost reduction and widespread deployment of optical fiber modules.